First is Sounga, Rhyela's other kitty. After I had released Tetsusaiga back in Wrath and was missing my kitty companion, I tried taming different kitties to try to find the same bond with another one. The only one that came close was a black panther from STV named Nemaeus (named tweaked from the Nemean lion). I loved the color, but the model just doesn't do anything for me, so I let him go.
When I found that Duskfang was being introduced in the game (though not tamable right away), I found myself hoping for Blizz to flip that proverbial switch. I love the mount model, and that black was just beautiful. I was very happy when they finally made him tamable, so I ran out and grabbed him and named him Sounga (after the sword Sō’unga in Inu Yasha, to keep with my "theme" that I never meant to have).
When I got Tetsusaiga back (<3), I briefly thought about letting Sounga go, but I really enjoyed him as a companion and still love his appearance. Even though I generally try not to have more than one of any pet family (though I'm not so good at actually sticking to that), I couldn't help but allow Sounga to remain. He'll never be as special as Tetsusaiga, but he's a good friend nonetheless.
My other kitty friend belongs to Ariela, my baby hunter on Lightbringer. I had sworn to not tame every single animal I came across, and to wait until the right one called to me. I assumed it would be a while before that happened. I even took up SV as a spec because I figured I'd have to be able to kill stuff without a pet for a while (I released my starter pet as soon as I was able). I assumed wrong. I couldn't even make it out of the starting zone without taming something. But, it wasn't just any something. It was a lynx. I don't know why this particular one pulled me so. I had tried lynxes before and didn't really care for them (couldn't help but see that model as a druid, since my druid had been that model for years). But this one was different somehow. I so cleverly came up with the name Purcival, after Percival from Arthurian legend. I made it "Pur" like "purr"...ha.

Anyway, the bond was instant. Purcival, again, has not touched me the way Tetsusaiga has, but he is a very close second, and he's definitely number one as far as Ariela is concerned. I can't seem to quest very long with another pet without missing him and pulling him out again. He's more than just a guardian or protector, he's also a friend and brother to Ariela. They both started out young, and as they grow together their bond only grows stronger. And Ariela protects him every bit as much as he protects her. They understand each other like no one else could.
